For a depressing ten minutes, click on the youtube link and read the comments. Pretty much entirely people slagging her off (although I have to admit "Swedish Doom Goblin" did make me chuckle Sorry Greta).
They are not making substantive critiques, just "Go back to school", "Why are we listening to her?", etc. Makes you wonder whether it's just random hordes of climate change denier trolls or paid flak or something else maybe? Whatever it is, it's depressing. We are so ####ed.